Osteoarthritis is by far the most common type of arthritis, with an estimated 12.1 percent of the U.S. population (nearly 21 million Americans) age 25 and older have osteoarthritis of one form or another. Although more common in older people, it usually is the result of a joint injury, a joint malformation, or a genetic defect in joint cartilage. The incidence and prevalence of osteoarthritis differs among various demographic groups: osteoarthritis tends to start for men before the age of 45, and after the age of 45 it is more common in women. It is also more likely to occur in people who are obese or overweight and is related to those jobs that stress particular joints.
Arthritis is a degenerative process that affects the musculoskeletal system and specifically the diarthrodal or synovial joints—where two or more bones meet and form a joint cavity surrounded by a synovial joint capsule. It often occurs in the joints of the hands and wrists (particularly in the fingers and thumbs, between the phalanges, the metacarpals and/or the carpals), feet (in the toes, between phalanges, metatarsals and/or tarsals), ankles, elbows, shoulders, knees, hips, and the spine (particularly at the neck and lower back). Joint problems can include inflammation and damage to joint cartilage (the tough, smooth tissue that covers the ends of the bones, enabling them to glide against one another) and surrounding structures. Such damage can lead to joint stiffness, weakness, instability and visible deformities that, depending on the location of joint involvement, can interfere with the basic daily activities such as walking, climbing stairs, using a computer keyboard, cutting food and brushing teeth. This ultimately results in moderate to severe pain. Drug regimes can provide temporary relief from the pain, but do not slow down the crippling affects. Drugs may also subject patients to serious side effects and risks, such as the increased cardiovascular risks associated with osteoarthritis drugs Vioxx and Bextra, which were withdrawn from the market. Drugs used to treat other forms of arthritis, such as corticosteroids, are associated with osteoporosis and hyperglycemia and can lead to increased risks of bone fracture and diabetes, for example. When pharmacologic therapy and physical therapy no longer provide adequate relief, only surgical options remain.
The treatment of severe arthritis may involve joint fusion, an open surgical procedure to implant a spacer, or to total joint replacement with a prosthetic device. Many of the current surgical treatments are not reversible. Current joint replacement therapies (spacers or a total prosthesis) require the joint capsule to be surgically opened and the bone surfaces to be partially or totally removed. Both modalities present various drawbacks. For example, U.S. Pat. No. 6,007,580 to Lehto et al. describes an implantable spacer that must be fixed at one or both ends to the bone of either end of the knuckle (e.g. the metacarpal-phalangeal (MCP) joint). The spacer must be implanted by opening of the joint capsule and be affixed at one or both ends to the corresponding bone surfaces.
Various spacers in the art can cause inflammation, while total joint replacement can limit the range of motion and also compromise the strength and stability of the joint. These surgeries are highly invasive and require the joint capsule to be surgically opened, and the incision itself can result in inflammation and infection. Due to the invasiveness of the procedure, prolonged healing times are required. Furthermore, the invasive nature of these surgeries sometimes precludes a second joint replacement or spacer when the first joint device wears out or fails.
It would be desirable as well as beneficial if there were an intermediary step or alternative treatment before subjecting patients to drastic joint replacement and/or long-term drug therapy.